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sixsevenco

Need guidance on Classic II repair

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1 minute ago, tanaquil said:

Definitely adjust it, but then check the 12V supply as well, if that is applicable to the Classic II (I know it works on the earlier compacts). If you can't adjust to 5V without throwing 12V out of whack, something is wrong on the component level.

 

From what I gather a voltage reading that far off is not uncommon. Hope a simple adjustment fixes it for you!

Yes. In my case pins 7 and 8 were at 12.06v. I think I’m in good shape. 

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2 minutes ago, tanaquil said:

Definitely adjust it, but then check the 12V supply as well, if that is applicable to the Classic II (I know it works on the earlier compacts). If you can't adjust to 5V without throwing 12V out of whack, something is wrong on the component level.

 

From what I gather a voltage reading that far off is not uncommon. Hope a simple adjustment fixes it for you!

I checked the 12V lines too, and it's also low. Pin 7 & 8 are reading about 11.5 V

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27 minutes ago, sixsevenco said:

I think you need a minimum of 4.85. I’ll bet you could get there by adjusting PP1. Do you have a tool that can safely reach it?

I don't but i'll look at buying one! The same item from Amazon Canada is over $338-o. Pffffft

 

I suppose as long as it's non-conductive and the same size as the longest one in that ST-13 kit, I should be good to go.

 

Will having low 12V cause issues too? It was reading about 11.5 V on the 12v line...

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9 minutes ago, javensbukan said:

I don't but i'll look at buying one! The same item from Amazon Canada is over $338-o. Pffffft

 

I suppose as long as it's non-conductive and the same size as the longest one in that ST-13 kit, I should be good to go.

 

Will having low 12V cause issues too? It was reading about 11.5 V on the 12v line...

Arg. That's a ridiculous price, especially for what it is...  Try searching for "Universal Color TV Alignment Tool" or something similar.  Maybe there's a different product that will accomplish the same thing.  I read somewhere that someone carved a bamboo kabob skewer for the task too.

 

 

 

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58 minutes ago, sixsevenco said:

Arg. That's a ridiculous price, especially for what it is...  Try searching for "Universal Color TV Alignment Tool" or something similar.  Maybe there's a different product that will accomplish the same thing.  I read somewhere that someone carved a bamboo kabob skewer for the task too.

 

 

 

I was able to whittle a bamboo kebab stick and adjust the P1 so that the voltage on the 5V line is reading about 4.8v now... however, the problem persists after a cold boot.

Guess next thing I'll have to do is replace the components mentioned in this thread earlier,... any thoughts on what one it might be.... guessing TDA4605 and CNY17G-3 as i've already replaced all of the caps.

 

I did notice that the 12V line is also reading higher since I adjusted P1, around 11.7 v, still well off from 12v, but an improvement from 11.5 I suppose.

Edited by javensbukan
Forgot the part numbers

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You should be able to get DP3, DP4, and CNY17G-3 from Mouser or Digikey.  I'd just get all of them.  With shipping, it would be less expensive to get all of them and maybe not use something.  You might need to go to ebay to find a TDA4605.  I couldn't find one in stock from a reputable online seller.  From what I read, DP3 and DP4 are a common point of failure, so you should definitely take care of them.

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On 8/2/2018 at 5:41 PM, javensbukan said:

Measured pin 6 and it's reading about 4.73 V.  Quite below 5V. Is that well within range of adjusting PP1?

 

Haven't replaced anything but caps, none of the Diodes or the DIPs have been replaced, just all of the capacitors.

 

I was just reading through "Mac classic & SE : repair and upgrade secrets" by Larry Pina, and I read the following which might be of help to you. Putting some fresh solder down on PP1 might just solve your problem!

 

Quote

If the display on the Mac Classic suddenly shrinks, gets
very dark, and there's a thin, white, vertical line about one
third of the way in from the left side; if there's poor linearity

and the right side begins to shake in and out in
time to disk drive activity, as shown in Figure 9-2, then
chances are there's a cracked or high resistance solder
joint on the Piher (pronounced pier) potentiometer at
board reference PP1.


To repair the problem, make sure the power cord is
physically disconnected from the computer, remove the
vinyl jacket from the analog board, and locate the
potentiometer. Set your Hakko 926 to 6000F. Add fresh
solder to the connections and the problem should be
fixed.


If not, then the potentiometer itself may be intermittent or
simply out of adjustment, although that's not likely. For a
temporary fix, set up your DMM as shown in Chapter 8,
Figure Insulate both the shaft and the handle of a #2
jeweler's screwdriver (with tape or shrink tubing) and turn
on the power. Working from the solder side of the analog
board, carefully adjust the pot for *4.95V to 5.05V. You
may find that the voltage swings wildly from one extreme
to the other (4.33V to 5.28V). In this case, working the
control (rapidly) back and forth a few times may allow it
to settle somewhere within the desired range. If not, then
the voltage adjustment potentiometer will have to be
replaced. For an exact replacement part, specify: Piher,
6mm carbon trimmer, 2200.

 

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sixsevenco good to hear you managed to resurrect  your mac from the dead, there is hope for us all.

I am slowly filling my basket on mouser thanks for advice regarding the capacitors, how do I find suitable replacements for DP3 and DP4, what are they? They do not have any markings.

 

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I'm still having some problems with my Classic II.  After replacing DP3, DP4, CNY17G-3, and TDA4605, everything was working perfectly for a few hours.  Voltages were rock steady.  After leaving the computer on for a few hours, voltages would start to drop.  I'd work on it some more, and voltages would return to normal only to drop after a period of time.

 

I've decided to replace all of the other capacitors on the analog board:

 

CF1
CF2
CF3
CF4
CL1
CL11
CL2
CP3
CP34
CP37
CV2

 

As I was removing these capacitors, I noticed that the RF2 resistor is chipped.  I am not sure if the fact that it's chipped will cause me any problems, but I would like to replace it.  I have really tried to teach myself how to read the markings on the resistor, but I don't fully understand them.  I would be most appreciative if someone here could help me identify a suitable replacement on mouser.com.  The markings are:

 

A (or is it a delta symbol) 1W

202G

16

 

I've attached pictures for reference.  Please help. :):)

 

 

IMG_1119.jpg

IMG_1120.jpg

Edited by sixsevenco

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Ok, so right after my last post, I remembered that my multi-meter can test resistance.  I hooked it up, and this is what it is showing.  I'm thinking that the resistor is functioning properly despite being chipped.  Thoughts?  Should I still replace it?

IMG_1121.jpg

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